1. Field of the Invention
The present invention relates to a sheet supply apparatus for supplying a sheet while automatically correcting inclined feeding of the sheet and a recording apparatus, and more in particular, to a sheet supply apparatus permitting a sheet to be set anywhere in the full range (random set) and a recording apparatus.
2. Description of the Related Art
The printer includes a printing head supported by a carrier and a platen opposed to the printing head, wherein a sheet is conveyed between the printing head and the platen by a pair of sheet conveyance rollers, and the sheet is printed by the printing head. The sheet can be supplied toward the sheet conveyance rollers automatically or manually.
A problem of inclined feeding of the sheet arises when a sheet is supplied toward the sheet conveyance rollers. Inclined feeding is liable to occur when the sheet is supplied by hand. Inclined feeding is a phenomenon in which a sheet is supplied with its upper end (the leading side of the sheet in the direction of conveyance) in an inclined position with respect to the sheet conveyance rollers. If the sheet is supplied to the sheet rollers in the inclined position, the sheet conveyance rollers convey the sheet to the printing head in the inclined position, so that the sheet cannot be neatly printed. Therefore, if a sheet is inclined when supplying a sheet, it is desirable to correct inclined feeding.
Japanese patent application No. 10-071644 which is earlier than to the present application discloses a sheet supply apparatus capable of correcting inclined feeding of the sheet. This sheet supply apparatus comprises a frame having a sheet conveyance surface, a shaft arranged rotatably above the sheet conveyance surface, a plurality of protrusions formed on the shaft in an axially spaced relationship and at circumferentially different angles, and a rotating unit for rotating the shaft, whereby the sheet is conveyed toward the sheet conveyance rollers in the printer along the sheet conveyance surface by the protrusions, so as to cause the sheet to abut against the sheet conveyance rollers to thereby correct inclined feeding.
In this sheet supply apparatus, in the case where the sheet is supplied inclined, one side end of the upper end (left end of the leading side of the sheet in the conveyance direction, for example) of the sheet comes into contact with the stationary sheet conveyance rollers. When one end of the sheet comes into contact with the sheet conveyance rollers, that one end of the sheet stops, and the other portion of the sheet continues to be conveyed by the protrusions of the shaft, so that the sheet rotates about the stopped end to thereby correct inclined feeding. In this case, it is the protrusions that convey and engage the sheet for rotating it. The protrusions do not restrict the sheet unlike a pair of pinch rollers, and therefore the sheet is easily and positively rotated thereby to correct the sheet diagonal travel.
A supply sensor is arranged to detect that a sheet is placed on the sheet conveyance surface of the sheet supply apparatus, so that the shaft begins to rotate and conveys the sheet while at the same time correcting inclined feeding thereof in response to the output of this supply sensor. This supply sensor is arranged at a position slightly to the left of the sheet supply apparatus. In the printer or the like, the sheet is usually set at a slightly left position, and the supply sensor arranged at a slightly left position can sufficiently detect the presence or the absence of the sheet placed on the sheet conveyance surface. However, there is a problem in which the supply sensor arranged at a slightly left position cannot detect a sheet if a sheet is set at a slightly right position or a small sheet is set at the center.